Diversity of parasitoids (Hymenoptera) associated with tephritids (Diptera) parasitising cucurbits in two agroecological zones of Cameroon, Central Africa

Abstract

Many parasitoid wasps (Hymenoptera) parasitise tephritids (Diptera), but little is known about the influence of host plants on this parasitism in sub-Saharan Africa. From June 2008 to January 2011, a study was conducted at three localities in two agroecological zones of Cameroon (Central Africa): Ngoa-Ekelé and Olembé (Southern Plateau) and Koutaba (Western Highlands), to assess the guild of parasitoids and their parasitism on tephritids attacking cucurbits. Data were collected on 3 249 fruits attacked of nine cucurbit species, from which were identified: 45 575 tephritids belonging to four species (Dacus bivittatus, D. ciliatus, D. punctatifrons, and D. vertebratus) and 3 330 parasitoids belonging to four families and 11 species of Hymenoptera. Most of the parasitoids collected were solitary koinobionts (mainly Braconidae - Opiinae (> 50%) and Eulophidae). The parasitism rate varied significantly between the localities (p < 0.001), with the lowest value obtained in Koutaba (4.98 ± 0.68%) and Ngoa-Ekelé (9.68 ± 0.54%), areas characterised by high agricultural activity and urbanisation respectively, and the highest in Olembé (23.93 ± 1.80%), a more natural area. Psyttalia perproxima and Tetrastichus dacicida were numerically abundant in all three localities, followed by Fopius spp. and Phaenocarpa sp. in Olembé. Regardless of the study localities, D. bivittatus and D. ciliatus were dominant and were parasitised by most of the parasitoids. Species richness and parasitism rates were higher on Cucurbita moschata fruits, while no parasitoid emerged from Sechium edule fruits. From a biological control perspective, the tephritid-parasitoid association was species-rich and included many potential tephritid biological control agents.